1. Technical Field
This disclosure relates generally to heat exchange systems and, more particularly, to a hybrid refrigeration system for a mobile unit.
2. Background Information
Heat exchange systems can be used to regulate environmental conditions within a mobile unit (e.g., a vehicle, a truck container, a truck trailer, a shipping container, etc.). Typically, heat exchange systems are powered either directly or indirectly by an internal combustion engine. The engine may be operated during high load conditions (e.g. when the heat exchange systems require/draw a relatively large quantity of power), during low load conditions (e.g. when the heat exchange systems require a relatively small quantity of power), and during idle conditions (e.g. when the heat exchange systems are idle and require no power).
In an effort to reduce energy consumption and costs associated therewith, it is known to operate the engine of a heat exchange system in an operational mode where the engine is subject to periods of operation and periods of rest. This mode of operation can be referred to as a “start and stop” mode of operation. One of the issues with the start and stop mode of operation is that when the engine is needed but the load on the heat exchange system is low, the engine may produce more power than the heat exchange system requires, which negatively effects the efficiency of the system. Another issue with the start and stop mode is that when the system is not operating, the air within the mobile unit is likely to be not circulating. As a result, localized thermal hotspots (and associated steep temperature variances) may form within the mobile unit. The formation of these hotspots can lead to inaccurate temperature readings and reduce the efficiency of the system. For example, if the temperature of the air proximate a sensor within the mobile unit is higher or lower than air elsewhere within the unit, the information provided by the sensor and any actions based on that information may be suspect. To reduce these inaccurate readings, some prior art systems “prime” the sensors within the mobile unit. The term “prime” is used to refer to scenarios where the prior art heat exchange system, including the engine, is run to circulate air within the mobile unit for a period of time until the temperature of the air within the mobile unit is more uniformly distributed. However, similar to low load conditions, the engine used to create the circulation typically produces more power than is required to “prime” the system and energy is consequently wasted. There is, therefore, a need in the art for a heat exchange system that reduces energy consumption during low load conditions.